yanmar 1 cyl diesel . too much black smoke

[feagin]

I have checked the exhaust for blockage short of pulling off the elbo where water is added. This is on a hunter 28 sailboat. With no load it revs up to 3400 rpm which says the govrenor is working. Under a load the max rpm is 1500 rpm and smokes bad and leves a trail of black unburmed fuel trialing behind the boat. My view is not enough air is getting in to the engine or there is a clog in the exhaust system. Isn't that usually what causes one to smoke like a pig. A yanmar service tech thinks it may be low compression. It starts easy and idles perfect. Any ideas or help would be great. Thank's Pat

 

[Don S]

Re: yanmar 1 cyl diesel . too much black smoke

Have you checked the air filter?

 

[feagin]

Re: yanmar 1 cyl diesel . too much black smoke

yep, ran it with out it. no change.

 

[feagin]

Re: yanmar 1 cyl diesel . too much black smoke

Don S. Do you think black smoke at full throtle could be a low compression problem even if it idles and starts great? Pat F.

 

[Don S]

Re: yanmar 1 cyl diesel . too much black smoke

A compression check will tell you if you have a low compression problem, with only one cylinder it shouldn't take long to do.<br />No experience with a 1 cylinder Yanmar, but it could also be a bad injector. Don't know what year your engine is or how many hours you have on it, but pop testing injectors should be a scheduled maintence type item, similar to a tuneup on a gas engine.

 

[QC]

Re: yanmar 1 cyl diesel . too much black smoke

If it runs 3400 no load and only 1500 under load, sumpin' else aint right. Most mechanical governors are around 10% difference between full speed no load and rated bhp RPM. Has it ever ran at higher RPM under load? Black is too much fuel for the available air, but it is still burning. A deep lug condition is what it sounds like to me which is like too much prop/load etc. Yes could be an injector, but I don't think so. It could even be in the governor despite the full speed no load number. Something aint lettin' her wind up yet the fuel is there.<br /><br />Low compression they will usually smoke white. White smoke is unburnt fuel . . . that's why they smoke white when cold.

 

[John Schlotzhauer]

Re: yanmar 1 cyl diesel . too much black smoke

A compression check will tell you if you have a low compression problem, with only one cylinder it shouldn't take long to do.<br />No experience with a 1 cylinder Yanmar, but it could also be a bad injector. Don't know what year your engine is or how many hours you have on it, but pop testing injectors should be a scheduled maintence type item, similar to a tuneup on a gas engine.

 

[John Schlotzhauer]

Re: yanmar 1 cyl diesel . too much black smoke

A compression check will tell you if you have a low compression problem, with only one cylinder it shouldn't take long to do.<br />No experience with a 1 cylinder Yanmar, but it could also be a bad injector. Don't know what year your engine is or how many hours you have on it, but pop testing injectors should be a scheduled maintence type item, similar to a tuneup on a gas engine.

This engine has a new injector and the compression check turned out to be within spec. Head has been rebuilt but engine still dumps fuel thru exhaust that has been replaced and mixer cleaned. Any suggestions?
John